Madness

• Cinema/Television: "Eaten Alive" (Tobe Hooper, 1976), "Midnight Ride" (Bob Bralver, 1990), "The Ward" (John Carpenter, 2010).
• Literature (fiction): "The System of Doctor Tarr and Professor Fether" (Edgar Allan Poe, 1845), "The Shining" (Stephen King, 1977), "American Psycho" (Bret Easton Ellis, 1991).
• Videogames: "Pathologic" (2006), "Far Cry 3" (2012), "Hellblade: Senua's Sacrifice" (2017).

"Madness" partially overlaps with the "Paranoia" Tag (paranoia essentially being a psychosis), but the "Madness" Tag won't be applied to films in which the pathological element is relegated to the background or proves to be altogether absent.

A couple of illustrative examples:

In "Invaders from Mars" (1953), it's clear from the get-go that the Martians have come to subjugate us, which explains why the film earns the "Paranoia" but not the "Madness" Tag. (As outlined in the "Paranoia" profile, that Tag includes cases in which the protagonist's suspicions turn out to be valid and not the result of insanity). The same thing applies to "Rosemary's Baby" (1968), where the conspiracy against the mother-to-be is decidedly genuine. Sticking with the Polanski oeuvre, it's a different case for "The Tenant" (1976), since the doubts and uncertainties that permeate the story don't allow for a definitive interpretation of the film's events, leaving the door open to the possibility that poor Trelkovsky really is suffering from paranoid psychosis. As a result, it receives both Tags, "Madness" and "Paranoia".

Finally, here's a brief clarification regarding the potential overlap between "Madness" and the "Doppelgänger" Tag, which also includes films dealing with dissociative disorders. Again, it all comes down to the amount of importance and screen time devoted to the "mental illness" theme.

A couple of illustrative examples:

In "Dr. Jekyll and Mr. Hyde" (1931), the protagonist's dissociation doesn't have a medical-scientific significance, being a clear metaphor for the battle between Good and Evil lurking within each of us. Ergo, the "Madness" Tag doesn't apply here. On the other hand, in "Psycho" (1960), the disorder affecting Norman Bates, with its profound psychoanalytic significance, lends itself to seen within a context of full-blown psychopathology. Thus, Hitchcock's masterpiece garners both the "Madness" as well as the "Doppelgänger" Tag.